Highest temperature in Hong Kong on August 9?

Platform comparison

Market context

Hong Kong’s highest temperature on 9 August will be set by the Hong Kong Observatory’s final “Absolute Daily Max” reading for the day, with the market resolving only after the Daily Extract is published. The current crowd-implied probability of **0% YES** suggests traders are treating this as a settled, low-volatility weather contract rather than a live pricing contest, although that does not by itself tell you which temperature band is most likely.

The historical frame points towards a late-summer Hong Kong peak usually sitting in the low-30s Celsius, with the Observatory’s August normals putting the 9 August daily mean maximum at **31.6°C** and nearby daily maxima in the high-20s to low-30s range. Recent official and news reporting also shows Hong Kong has already posted very hot readings this year, including a **34.7°C** Observatory high on 8 August 2026, which makes another warm outcome plausible if the same regional heat persists into the settlement window. Timeanddate’s forecast for 9 August shows a daytime high of **96°F** (about **35.6°C**), while AccuWeather’s Hong Kong page points to **100°F** (about **37.8°C**), implying that sportsbook-style weather pricing, where available, may sit materially above a zeroed prediction-market line. [5][8][12][14]

For traders, the main catalysts are the Observatory’s morning forecast updates, the actual hourly readings through the day, and the timing of the final Daily Extract publication, since the contract cannot resolve until that dataset is posted. The practical dependency is straightforward: if cloud cover, rain bands or a shift in onshore flow suppress the afternoon maximum, the settling band can fall back towards the low 30s; if heat intensifies before the 12:00 UTC window closes, the upper-30s bands become more relevant. The official weather forecast and hourly readings on the Hong Kong Observatory site are therefore the key live reference points, with the eventual resolution anchored to the published Observatory maximum rather than any third-party forecast line. [2][11]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is PolyGram. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.